Display device and backlight unit included therein

ABSTRACT

A display device includes a display panel, a backlight unit outputting light to the display panel, and an optical member refracting or reflecting the light output from the backlight unit and providing the display panel with the light. The backlight unit includes a light source emitting the light, a light guide plate scattering the light emitted from the light source and irradiating the scattered light to a front surface of the backlight unit, a reflective sheet reflecting the light, which is irradiated to a rear surface of the light guide plate, to the light guide plate, a quantum dot sheet for converting the light, which is irradiated to the front surface of the light guide plate, into a white light, and a light-converting material provided on an edge portion of the reflective sheet to convert the light into the white light.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2015-0007377, filed on Jan. 15, 2015 in the Korean IntellectualProperty Office, and U.S. Provisional Application No. 62/089,469, filedin the U.S. Patent and Trademark Office on Dec. 9, 2014, the disclosuresof which are incorporated herein by reference.

BACKGROUND

1. Field

Exemplary embodiments relate to a display device, and more particularly,to a display device including an edge type backlight unit.

2. Description of the Related Art

A display device is a device which includes a display panel to displayan image of a broadcast signal or various formats of image data.

The display panel may be an emissive display panel which emits light byitself and a non-emissive display panel which does not emit the light byitself. The emissive display panel includes a cathode ray tube (CRT)panel, an electro-luminescence (EL) panel, an organic light emittingdiode (OLED) panel, a vacuum fluorescence display (VFD) panel, a fieldemission display (FED) panel, a plasma display panel (PDP), etc., andthe non-emissive display panel includes a liquid crystal display (LCD)panel, etc.

The liquid crystal display panel includes a backlight unit emitting awhite light and a display panel transmitting or blocking the lightemitted from the backlight unit.

In particular, it is important for the liquid crystal display panel tohave uniform brightness and uniform color tone on an entire surface. Inorder to achieve the above, the backlight unit should irradiate lighthaving a uniform brightness and a uniform color tone on an entiresurface.

Due to a structural difference between an edge portion and a centralportion of the backlight unit, however, the brightness and color tone ofthe light irradiated from the edge portion differ from the brightnessand color tone of the light irradiated from the central portion.

SUMMARY

It is an aspect of the exemplary embodiments to provide a display deviceand a backlight unit which minimize a difference between brightness oflight irradiated from an edge portion and brightness of light irradiatedfrom a central portion and a difference between a color tone of thelight irradiated from the edge portion and a color tone of the lightirradiated from the central portion.

A display device according to an exemplary embodiment includes a displaypanel, a backlight unit outputting light to the display panel, and anoptical member configured to refract or reflect the light output fromthe backlight unit and provide the display panel with the refracted orreflected light, and the backlight unit includes a light source emittingthe light, a light guide plate configured to scatter the light emittedfrom the light source and irradiate the scattered light to a frontsurface of the backlight unit, a reflective sheet configured to reflectthe light, which is irradiated to a rear surface of the light guideplate, to the light guide plate, a quantum dot sheet configured toconvert the light, which is irradiated to the front surface of the lightguide plate, into a white light, and a light-converting materialprovided on an edge portion of the reflective sheet for converting thelight at the edge portion of the reflective sheet into the white light.

According to an exemplary embodiment, the light-converting material mayinclude a fluorescent material.

According to an exemplary embodiment, the light-converting material maybe applied to the reflective sheet.

According to an exemplary embodiment, the light-converting material maybe applied to the reflective sheet in an area defined by a widthextending from a first end of the reflective sheet to a central portionof the reflective sheet.

According to an exemplary embodiment, an area of the appliedlight-converting material may be decreased as a distance from the firstend of the reflective sheet to the central portion of the reflectivesheet is increased

According to an exemplary embodiment, a concentration of thelight-converting material may be decreased as a distance from the firstend of the reflective sheet to the central portion of the reflectivesheet is increased.

According to an exemplary embodiment, the light-converting material maybe applied in a circular pattern to the reflective sheet.

According to an exemplary embodiment, the light-converting material maybe applied in a polygonal pattern to the reflective sheet.

According to an exemplary embodiment, the light-converting material maybe applied in a stripe pattern to the reflective sheet.

According to an exemplary embodiment, the light-converting material maybe applied to the light guide plate.

According to an exemplary embodiment, the light-converting material maybe applied to the quantum dot sheet.

According to an exemplary embodiment, the backlight unit may furtherinclude an optical sheet including the light-converting material on anedge portion thereof.

According to an exemplary embodiment, the optical sheet may be providedbetween the reflective sheet and the light guide plate.

According to an exemplary embodiment, the optical sheet may be providedbetween the light guide plate and the quantum dot sheet.

According to an exemplary embodiment, the optical sheet may be providedbetween the optical member and the quantum dot sheet.

A backlight unit according to an exemplary embodiment includes a lightsource emitting light, a light guide plate scattering the light emittedfrom the light source and irradiating the scattered light to a frontsurface of the backlight unit, a reflective sheet reflecting the light,which is irradiated to a rear surface of the light guide plate, to thelight guide plate, a quantum dot sheet converting the light, which isirradiated to the front surface of the light guide plate, into a whitelight, and a light-converting material provided on an edge portion ofthereof for converting the light into the white light at the edgeportion of thereof.

According to an exemplary embodiment, the light-converting material mayinclude a fluorescent material.

According to an exemplary embodiment, the light-converting material maybe applied to the reflective sheet.

According to an exemplary embodiment, the light-converting material maybe applied to the reflective sheet in an area defined by a widthextending from a first end of the reflective sheet to a central portionof the reflective sheet.

According to an exemplary embodiment, an area of the appliedlight-converting material may be decreased as a distance from the firstend of the reflective sheet to the central portion of the reflectivesheet is increased.

According to an exemplary embodiment, a concentration of thelight-converting material may be decreased as a distance from the firstend of the reflective sheet to the central portion of the reflectivesheet is increased.

A backlight unit according to an exemplary embodiment includes a lightsource to emit light, a light guide plate to scatter the light, areflective sheet provided on the light guide plate to reflect the light;and a quantum dot sheet to output the light as a white light, where alight-converting material is provided on the backlight unit to convertthe light at an edge portion of the backlight unit into the white light.

According to an exemplary embodiment, the backlight unit also includesan optical sheet provided on a front side of the quantum dot sheet andto irradiate visible light.

According to an exemplary embodiment, the light-converting material isprovided on one from among the quantum dot sheet, the reflective sheet,and the optical sheet.

According to an exemplary embodiment, the light-converting material isprovided on an area defined by an edge of the backlight unit and acentral portion of the backlight unit.

According to an exemplary embodiment, the light-converting materialincludes a plurality of circles, the largest circles being at the edgeof the backlight unit and decreasing in size toward the central portionof the backlight unit, with a space between the plurality of circles.

According to an exemplary embodiment, it is possible to provide thedisplay device and the backlight unit which is provided with thelight-converting material on the edge portion of the backlight unit tominimize a difference between the brightness of the light irradiatedfrom the edge portion and the brightness of the light irradiated fromthe central portion and a difference between the color tone of the lightirradiated from the edge portion and the color tone of the lightirradiated from the central portion.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of exemplary embodiments,taken in conjunction with the accompanying drawings of which:

FIG. 1 is a view showing an external appearance of a display deviceaccording to an exemplary embodiment;

FIG. 2 is an exploded view of a display device according to an exemplaryembodiment;

FIG. 3 is a view showing a side sectional view of a display deviceaccording to an exemplary embodiment;

FIG. 4 is a view showing a light recycling at a central portion of adisplay device according to an exemplary embodiment;

FIG. 5 is a view showing blue light output from an edge portion of adisplay device according to an exemplary embodiment;

FIG. 6 is a view showing a process for compensating blue light outputfrom an edge portion of a display device according to an exemplaryembodiment;

FIG. 7 shows two views, (a) and (b) of a light-converting material beingapplied to a reflective sheet of a display device according to anexemplary embodiment;

FIG. 8 shows two views, (a) and (b), showing a density of alight-converting material applied to a reflective sheet of a displaydevice according to an exemplary embodiment;

FIG. 9 shows four views, (a), (b), (c), and (d), showing a pattern of alight-converting material applied to a reflective sheet of a displaydevice according to an exemplary embodiment;

FIG. 10 is a view comparing a color coordinate of a display deviceaccording to an exemplary embodiment with a conventional display device;

FIG. 11 is a view showing a side section of a display device accordingto an exemplary embodiment;

FIG. 12 is a view showing a side section of a display device accordingto an exemplary embodiment;

FIG. 13 is a view showing a side section of a display device accordingto an exemplary embodiment;

FIG. 14 is a view showing a side section of a display device accordingto an exemplary embodiment; and

FIG. 15 is a view showing a side section of a display device accordingto an exemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout. However, knownfunctions associated with the exemplary embodiments or detaileddescriptions on the configuration and other matters which wouldunnecessarily obscure the present disclosure will be omitted.

FIG. 1 is a view showing an external appearance of a display deviceaccording to one embodiment of the disclosure, FIG. 2 is an explodedview of a display device according to one embodiment of the disclosure,and FIG. 3 is a side sectional view of a display device according to oneembodiment of the disclosure.

The display device 1 is a device which can process an image signalreceived from the outside and visually display the processed imagethereon. Hereinafter, although a television is described as one exampleof the display device 1, the disclosure is not limited thereto. Forexample, the display device 1 according to the disclosure may berealized as various forms of display devices such as a monitor, aportable multimedia device, a mobile telecommunication device, and thelike, and if the display device 1 is a device which visually displays animage, the form thereof is not limited.

Referring to FIGS. 1-3, a display device 1 includes a main body 10configured to accommodate various parts and a display panel 20 fordisplaying an image to a user U. In addition, a driving circuit 30, abacklight unit (BLU) 50, and an optical member 40 are provided in themain body 10.

The main body 10 may include a top chassis 11 provided on a front faceof the display device 1, a bottom chassis 13 provided on a rear face ofthe display device, and a mold frame 15 provided in the display device1.

The top chassis 11 is provided on a surface which is the same as asurface, on which the image is displayed, of the display panel 20 toprevent an edge portion of the display panel 20 from being exposed to anoutside.

The bottom chassis 13 may be provided on a side opposite the displaypanel 20 to prevent various kinds of structural elements included in thedisplay device 1 from being exposed to the outside, and protects thevarious structural elements included in the display device 1 from anexternal shock.

The mold frame 15 limits movements of the display panel 20, the opticalmember 40, and the backlight unit 50, and secures the display panel 20,the optical member 40, and the backlight unit 50 to the top chassis 11and the bottom chassis 13.

The display panel 20 may display a variety of images according to theimage signal input from the outside. The display panel 20 may be anemissive display panel in which a plurality of pixels constituting thedisplay panel 20 emits light to generate an image or may be anon-emissive display panel in which a plurality of pixelsreflect/transmit/block the light to generate the image.

Hereinafter, according to an exemplary embodiment, the display panel 20is the non-emissive display panel in which the light emitted from thebacklight unit 50 is reflected/transmitted/blocked to generate theimage.

The display panel 20 may include a liquid crystal layer (not shown), atransparent electrode layer (not shown), a transparent substrate (notshow), and a color filter array (not shown).

The liquid crystal layer contains an adequate amount of liquid crystal.The liquid crystal means an intermediate phase of crystal and liquid.Such liquid crystal may exhibit an optical property according to achange of a voltage. For example, the arrangement direction of moleculesconstituting the liquid crystal may be changed according to a change ofan electric field applied to the liquid crystal.

A pair of transparent electrode layers are provided at both sides of theliquid crystal layer for forming the electric field on the liquidcrystal layer. The electric field applied to the liquid crystal layer ischanged is changed according to the voltage applied between the pair oftransparent electrode layers.

The aforementioned transparent electrode layer may include a gate line(not shown), a data line (not shown), and a thin film transistor (TFT).

The gate line is arranged in a row direction to turn on or turn off thethin film transistor, and the data line is arranged in a columndirection to transmit a data signal to the plurality of pixels throughthe thin film transistor. The electric field applied to the liquidcrystal layer is changed according to a gate signal input through thegate line and the data signal input through the data line. The moleculararrangement of the liquid crystal is changed according to the change ofthe electric field. In addition, the light is transmitted through theliquid crystal layer or is blocked according to the moleculararrangement of the liquid crystal.

The gate line and the data line may be formed of indium tin oxide (ITO)or indium zinc oxide (IZO).

A pair of transparent substrates (not shown) form an external appearanceof the display panel 20 and protect the liquid crystal layer and thetransparent electrode layer. Such transparent substrates may be formedof tempered glass or a transparent film having an excellent lighttransmittance.

The color filter array may include a red color filter, a blue colorfilter, and a green color filter formed on areas corresponding to thepixels, respectively, so as to allow each of the plurality of pixelsconstituting the display panel 20 to show the colors.

As described above, the display panel 20 blocks or transmits the lightemitted from the backlight unit 50 to generate the image. Specifically,each of the pixels constituting the display panel 20 blocks or transmitsthe light of the backlight unit 50 to generate the image having variouscolors.

The driving circuit 30 provides the display panel 20 with a drivingsignal for driving the display panel 20. The driving circuit 30 mayinclude a gate driving circuit 31 and a data driving circuit 33.

The gate driving circuit 31 may be connected to the gate line (notshown) of the display panel 20 to transfer the gate signal to the gateline. Also, the data driving circuit 33 may be connected to the dataline (not shown) of the display panel 20 to transfer the data signal tothe data line.

The backlight unit 50 is installed at a rear side of the display panel20 and emits the light for generating the image. The backlight unit 50may be classified into an edge type backlight unit (BLU) in which alight source is placed at a side surface and a direct type backlightunit (BLU) in which the light source is placed at a rear side of thedisplay panel 20.

Hereinafter, the edge type backlight unit in which the light source isplaced at the side surface will be described as the backlight unit 50.

As shown in FIG. 3, the backlight unit 50 includes a light source 51, alight guide plate (LGP) 53 configured to convert the light emitted fromthe light source 51 into a sheet light, a reflective sheet 55 providedon a rear surface of the light guide plate 53 to reflect the lightirradiated from the light guide plate 53, and a quantum dot sheet 57receiving the light from the light guide plate 53 and outputting a whitelight (in which various color lights are mixed).

As shown in FIG. 3, the light source 51 is provided on a side surface ofthe light guide plate 53 to emit the light towards the light guide plate53.

The light source 51 may emit the light (the monochromatic light) with asingle wavelength (single color) or may emit the light (the white light)in which a plurality of lights with a plurality of wavelengths whichdiffer from each other are mixed. In general, in the case in which thebacklight unit 50 includes the quantum dot sheet 57, a light sourceemitting the monochromatic light (in particular, a blue-colored lightwith a short wavelength) is used as the light source. Hereinafter, alight source emitting the blue-colored light (hereinafter, “blue light”)is described as the light source 51.

A light emitting diode (LED) or a cold cathode fluorescence lamp (CCFL)with a low calorific value may be employed as the light source 51.

In the edge type backlight unit 50, the light guide plate 53 changes theadvancing direction of the light incident from a side surface and thenirradiates the light towards a front surface. In order to change theadvancing direction of the light, the light guide plate 53 may have aplurality convex stripes formed on a front surface 53 a thereof and aplurality of dots formed on a rear surface 53 b thereof. Also, in orderto allow the light to be uniformly irradiated to the front surface 53 aof the light guide plate 53, a dimension of the convex stripe and a gapbetween the stripes may be adjusted and a dimension of the dot and a gapbetween the dots may be adjusted.

In addition, the convex stripe on the front surface 53 a of the lightguide plate 53 may be convexly formed by a printing method and the doton the rear surface 53 b of the light guide plate 53 may be concavelyformed by a laser.

As shown in FIG. 3, a part L1 of the light incident on the light guideplate 53 is scattered by the dots formed on the rear surface 53 b of thelight guide plate 53 and may be irradiated to the front surface 53 a ofthe light guide plate 53, and another part L2 of the light incident onthe light guide plate is reflected into the light guide plate 53 by thereflective sheet 55 provided on the rear surface 53 b of the light guideplate 53. In addition, the reflected part L2 may be irradiated to acentral portion of the light guide plate 53, and may be scattered at thecentral portion of the light guide plate 53 and then irradiated to thefront surface 53 a of the light guide plate 53.

Due to the refraction, reflection, and scattering of the light in thelight guide plate 53, the light guide plate 53 may irradiate the uniformlight to the front surface thereof.

The aforementioned light guide plate 53 may be formed ofpolymethylmethacrylate (PMMA) or transparent polycarbonate (PC) which istransparent and has an excellent strength.

The reflective sheet 55 is provided on the rear surface 53 b of thelight guide plate 53 described above. In the light guide plate 53, thereflective sheet 55 reflects some of the light which is being irradiatedtoward the rear surface of the light guide plate 53 into the light guideplate 53.

The reflective sheet 55 is fabricated by coating a base material with amaterial having a high reflectivity. For example, the reflective sheet55 may be fabricated by coating a base material such as polyethyleneterephthalate (PET) with a polymer having a high reflectivity.

As shown in FIG. 3, a light-converting material 101 is applied to anedge portion of the reflective sheet 55. The light-converting material101 is a material which emits visible light when the light is incidentfrom the outside and may include a fluorescent material or a quantumdot.

Once the light is incident from the light guide plate 53 to the edgeportion of the reflective sheet 55, some of the incident light isconverted into the white light by the light-converting material 101, andthe light reflected by the reflective sheet 55 and the white lightconverted by the light-converting material 101 are irradiated together.

The light-converting material 101 applied to the edge portion of thereflective sheet 55 will be described in more detail below.

The quantum dot sheet 57 converts the light irradiated to the frontsurface 53 a of the light guide plate 53 into the white light.

The quantum dot means a small-spherical shaped semiconductor particlehaving being a nanometer (nm, 1/1,000,000,000 meter) in size, and mayinclude a central body with a size of approximately 2 nanometers [nm] to10 [nm] and a shell formed of zinc sulfide (ZnS). Cadmium selenide(CdSe), cadmium telluride (CdTe), or cadmium sulfide (CdS) may beemployed as a material for the central body of the quantum dot.

Once voltage is applied, the quantum dot emits the light by itself orabsorbs the light to emit the light with a specific wavelength.

An electron of the quantum dot in a stable state is located at a lowenergy level (or a low energy band). At this time, once the quantum dotabsorbs the light from the outside, the electron at the low energy levelis transferred to a high energy level (or a high energy band). Since theelectron at the high energy level is unstable, the electron is naturallytransferred from the high energy level to the low energy level. During atransfer from the high energy level to the low energy level, theelectron emits the light corresponding to an energy difference betweenthe high energy level to the low energy level. A wavelength of theemitted light is determined by the energy difference between the highenergy level to the low energy level.

A size of the quantum dot may be proportional to a wavelength of thelight to be emitted. For example, the quantum dot having a diameter of 2nanometers [nm] may emit the blue-colored light and the quantum dothaving a diameter of approximately 10 nanometers [nm] may emit ared-colored light.

In addition, by using the quantum dots having various sizes, it ispossible for the quantum dots to emit light of varying wavelengths fromthe red light to the blue light. Once the quantum dots having varioussizes are employed, the light having a natural color (white light) canbe generated.

The quantum dot sheet 57 may be manufactured by distributing the quantumdots on resin.

Once the light is incident from the light guide plate 53 to the quantumdot sheet 57, the incident light excites the electron of the quantum dotcontained in the quantum dot sheet 57. In other words, the electron atthe low energy level (or the low energy band) is transferred to the highenergy level (or the high energy band) by the incident light.

Subsequently, while the excited electron is transferred from the highenergy level to the low energy level, the quantum dot emits the light(the white light) with various wavelengths. The light having variouswavelengths may pass through the optical member 40 and the display panel20 to generate the image.

The backlight unit 50 may include the light source 51, the light guideplate 53, the reflective sheet 55, and the quantum dot sheet 57 toirradiate a uniform sheet light.

The optical member 40 refracts or scatters the light so as to widen aviewing angle of the display device 1 and to enhance brightness of thedisplay device 1.

The optical member 40 may include a variety of sheets. For example, theoptical member 40 may include a diffusion sheet 41, a prism sheet 43, aprotective sheet 45, and a dual brightness enhancement film (DBEF) 47.

The diffusion sheet 41 diffuses the light emitted from the backlightunit 50 along a surface to make a color and brightness on a screen ofthe display device 1 entirely uniform. Since the light irradiated fromthe light guide plate 53 is irradiated through patterns formed on thefront surface 53 a of the light guide plate 53, the patterns formed onthe front surface 53 a of the light guide plate 53 is visible from thelight irradiated from the light guide plate 53.

In order to prevent the patterns formed on the front surface 53 a of thelight guide plate 53 from being seen from the light irradiated from thelight guide plate 53, the diffusion sheet 41 diffuses the irradiatedlight from the light guide plate 53 in a direction which isperpendicular to the irradiation direction.

The diffusion sheet diffuses the light emitted from the backlight unit50 to uniformly maintain the brightness on the entire surface.

Since the light having passed through the diffusion sheet 41 is diffusedin the direction perpendicular to a surface of the diffusion sheet 41,the brightness is rapidly decreased. The prism sheet 43 refracts orcollects the light diffused by the diffusion sheet 41 to increase thebrightness.

In addition, the prism sheet 43 includes a triangular prism-shaped prismpattern and a plurality of prism patterns are adjacently disposed toeach other to form a plurality of bands. The prism patterns form linesin the form of a pattern in which hills and valleys are alternately andrepeatedly disposed, and protrude toward the display panel 20.

The protective sheet 45 protects all kinds of structural elementsincluded in the backlight unit 50 from an external shock or an inflow offoreign substances. In particular, a scratch is easily generated on theprism sheet 43 and the protective sheet 45 prevents this scratch frombeing generated on the prism sheet 43.

The dual brightness enhancement film 47 is one kind of a polarizing filmand is also called a reflective polarizing film. Such a dual brightnessenhancement film 47 transmits polarized light in the light irradiatedfrom the backlight unit 50, which is parallel to a polarizationdirection of the dual brightness enhancement film 47, and reflects thelight which is polarized in a direction opposite to the polarizationdirection of the dual brightness enhancement film 47.

It is known that the light is a transverse wave which is vibrated in adirection perpendicular to an advancing direction of the light. When thelight is vibrated in various directions, the light vibrated in aspecific direction is transmitted through a polarizing film and thelight vibrated in another direction is absorbed by the polarizing film.

As compared with the polarizing film, the dual brightness enhancementfilm 47 reflects the light which is polarized in the direction oppositeto the polarization direction of the dual brightness enhancement film47. Here, the reflected light is recycled in the backlight unit 50 andthe brightness of the display device 1 is enhanced by the lightrecycling.

The light recycling is described in detail below.

FIG. 4 shows the light recycling at a central portion of the displaydevice according to an exemplary embodiment.

As shown in FIG. 4, various optical phenomena are generated at thecentral portion of the display device 1.

As previously described, lights L3 and L4 scattered on the rear surface53 b of the light guide plate 53 are irradiated toward the quantum dotsheet 57.

At this time, at least some of light L3 irradiated from the light guideplate 53 is absorbed in the quantum dot sheet 57, and the light mayexcite the electron contained in the quantum dot of the quantum dotsheet 57. While returning to the stable state, the electron of thequantum dot, which is excited by the light, may irradiate the light withvarious wavelengths (the white light).

Due to at least some of light L3 of the lights L3 and L4 beingirradiated from the light guide plate 53, the quantum dot sheet 57 mayirradiate the while light.

In addition, another light L4 of the lights L3 and L4 irradiated fromthe light guide plate 53 is not absorbed in the quantum dot sheet 57,but may be transmitted through the quantum dot sheet 57. Since thequantum dot sheet 57 is manufactured by distributing the quantum dots onthe resin, a sufficient space is formed between the quantum dots so thatthe light irradiated from the light guide plate 53 may be transmittedthrough the quantum dot sheet 57 via the space between the quantum dots.

As described above, the light irradiated from the quantum dot sheet 57includes the white light generated by the quantum dot sheet 57 and thelight transmitted through the quantum dot sheet 57. If the lightirradiated from the light guide plate 53 is the blue light emitted fromthe light source 51, the light irradiated from the quantum dot sheet 57also becomes the light including a blue color.

Some of light L5 of lights L5, L6, and L7 irradiated from the quantumdot sheet 57 may be transmitted through the optical member 40 and thedisplay panel 20 and may be output to the outside of the display device1. Specifically, the light L5 polarized in the direction which is sameas the polarization direction of the dual brightness enhancement film 47included in the optical member 40 may be transmitted through the opticalmember 40 and may be output to the outside of the display device 1 bydriving the display panel 20.

The light L5 output to the outside of the display device 1 may form theimage to be output by the display device 1.

In addition, some of lights L6 and L7 of the lights L5, L6, and L7irradiated from the quantum dot sheet 57 are reflected from the dualbrightness enhancement film 47 and are then incident on the backlightunit 50 again. Specifically, the lights L6 and L7 polarized in adirection which differs from the polarization direction of the dualbrightness enhancement film 47 included in the optical member 40 arereflected from the dual brightness enhancement film 47 and are incidenton the backlight unit 50.

Some of light L6 of the lights L6 and L7 reflected from the opticalmember 40 and entering the backlight unit 50 is absorbed in the quantumdot sheet 57 and may excite the electron included in the quantum dot ofthe quantum dot sheet 57. Also, while returning to the stable state, theelectron of the quantum dot, which is excited by the light, mayirradiate the lights with various wavelengths (the white light).

Some light L7 of the lights L6 and L7 reflected from the optical member40 and entering the backlight unit 50 is not absorbed in the quantum dotsheet 57 and may be transmitted through the quantum dot sheet 57.Specifically, the light reflected from the optical member 40 may betransmitted through the quantum dot sheet 57 via the space between thequantum dots included in the quantum dot sheet 57.

The light reflected from the dual brightness enhancement film 47 andentering the backlight unit 50 may be recycled in the backlight unit 50to enhance the luminance of the backlight unit 50.

While the light is recycled, the light passes repeatedly through thequantum dot sheet 57. In addition, some of lights L3 and L6 of thelights L3, L4, L6, and L7 are absorbed in the quantum dot of the quantumdot sheet 57, and the quantum dot sheet 57 may irradiate the white lightdue to the light absorbed in the quantum dot.

In other words, while the light is recycled in the backlight unit 50,the white light is gradually increased.

In general, the light source 51 of the backlight unit 50 emits themonochromatic light (in particular, the blue light) with a singlewavelength (single color). Although the light which is initially emittedfrom the light source 51 is the monochromatic light, the monochromaticlight is gradually converted into the white light while the light isrecycled in the backlight unit 50, in which the lights with variouswavelengths (various colors) are mixed.

As a result, most of the lights output from the backlight unit 50 becomethe white light.

Since the white light includes the lights with a plurality ofwavelengths (various color), it is possible to enhance a colorreproduction range of the display device 1.

In this way, the backlight unit 50 can output the white color throughthe light recycling at the central portion of the display device 1. Dueto a lack of the light recycling, the white light including the bluecolor may be output from the edge portion of the display device 1.

FIG. 5 shows the blue light output from the edge portion of the displaydevice according to an exemplary embodiment, and FIG. 6 shows a processfor compensating the blue light output from the edge portion of thedisplay device according to an exemplary embodiment.

The edge portion is a portion between the edge of the backlight unit 50,the light guide plate 53, the reflective sheet 55, and the quantum dotsheet 57, and a portion spaced apart from the above edge at a specificdistance toward a center of the above member. A width of the edgeportion of the backlight unit 50, the light guide plate 53, thereflective sheet 55, and the quantum dot sheet 57 is not a predeterminedvalue, but may be varied according to widths of the backlight unit 50,the light guide plate 53, the reflective sheet 55, and the quantum dotsheet 57.

The light recycling which is previously described is also generated atthe edge portion of the display device 1. Some of the light irradiatedfrom the quantum dot sheet 57 is reflected by the dual brightnessenhancement film 47 of the optical member 40 at the edge portion of thedisplay device 1 and some of the light transmitted through the quantumdot sheet 57 is converted into the white light.

However, the light recycling at the edge portion of the display device 1is less than that at the central portion of the display device 1.

At the edge portion of the display device 1, as shown in FIG. 5, somelight L8 of the recycled light may be irradiated to a side surface ofthe light guide plate 53 and some light L9 of the recycled light may beabsorbed by the mold frame 15. At the edge portion of the display device1, some of lights L8 and L9 of the recycled light is not irradiated tothe front surface 53 a of the light guide plate 53, and instead becomeslost.

Therefore, the white light generated by the light recycling is decreasedat the edge portion of the display device 1.

As shown in FIG. 5, some of light L10 of the monochromatic light (theblue light) emitted from the light source 51 may pass through the lightguide plate 53, the quantum dot sheet 57, the optical member 40, and thedisplay panel 20 at the edge portion of the display device 1, and bethen irradiated to the outside of the display device 1.

In the light irradiated from the display device 1, as a result, a ratioof the white light caused by the light recycling is decreased and aratio of the monochromatic light (the blue light) emitted from the lightsource 51 is increased. In addition, the image output from the displaydevice 1 looks blue at the edge portion of the display device 1.

If the ratio of the white light is decreased and the ratio of themonochromatic light (the blue light) is increased in the lightirradiated from the edge portion of the display device 1 as above, adifference of the color (a color coordinate) between the lightirradiated from the edge portion of the display device 1 and the lightirradiated from the central portion of the display device 1 isgenerated.

For example, when the light source 51 emits the blue light, as comparedwith the central portion of the display device 1, the edge portion ofthe display device 1 looks more blue. This phenomenon is called a Muraeffect of the display device 1.

In order to prevent the Mura effect, as shown in FIG. 6, thelight-converting material 101 may be applied to the edge portion of thereflective sheet 55. Here, the fluorescent material or the quantum dotwhich emits a light having a specific wavelength when the light isincident from the outside may be employed as the light-convertingmaterial 101.

Specifically, an electron of the light-converting material 101 in astable state is located at a low energy level (or a low energy band),and once the light-converting material 101 absorbs the light from theoutside, the electron at the low energy level is transferred to a highenergy level (or a high energy band). Since the electron at the highenergy level is unstable, the electron is naturally transferred from thehigh energy level to the low energy level. During a transfer from thehigh energy level to the low energy level, the electron emits energy inthe form of light. Also, a wavelength of the emitted light is determinedby an energy difference between the high energy level and the low energylevel.

When the light emitted from the light source 51 or the light recycled inthe backlight unit 50 is absorbed in the light-converting material 101,the light-converting material 101 cannot irradiate the light.

If the light-converting material 101 can irradiate a yellow light andthe red light, the yellow light and the red light irradiated from thelight-converting material 101 and the blue light transmitted through thelight-converting material 101 are mixed to irradiate the white lightfrom the light-converting material 101.

When the blue light is incident toward the light-converting material 101from the light source 51 as shown in FIG. 6, the light-convertingmaterial 101 may generate the yellow light and the red light using theblue light. Also, some of the blue light emitted from the light source51 may be transmitted through the light-converting material 101.

The yellow light and the red light generated by the light-convertingmaterial 101 is mixed with the blue light transmitted through thelight-converting material 101 so that light L12 irradiated from thelight-converting material 101 becomes the white light with variouswavelengths (various colors).

The white light generated by the light-converting material 101 appliedto the edge portion of the reflective sheet 55 may increase the ratio ofthe white color at the edge portion of the backlight unit 50. In otherwords, the light-converting material 101 applied to the edge portion ofthe reflective sheet 55 may compensate for a lack of the light recyclingat the edge portion of the backlight unit 50.

In order to compensate for the lack of the light recycling at the edgeportion of the backlight unit 50, the light-converting material 101 isapplied to the edge portion of the reflective sheet 55 included in thebacklight unit 50.

In addition, although the light-converting material 101 applied to afront surface of the reflective sheet 55 is described above, thedisclosure is not limited thereto, and the light-converting material 101may be applied to the rear surface 53 b of the light guide plate 53. Inother words, the light-converting material 101 may be located betweenthe light guide plate 53 and the reflective sheet 55.

A pattern of the light-converting material 101 applied to the edgeportion of the reflective sheet 55 is described below.

FIG. 7 shows one example in which the light-converting material isapplied to the reflective sheet of the display device according to anexemplary embodiment.

As shown in view (a) of FIG. 7, the light-converting material 101 may beapplied to a region of the edge portion of the reflective sheet 55,which is adjacent to the light source 51. The light-converting material101 is applied to this region because there is a lack of the lightrecycling at the edge portion of the backlight unit 50, whichcorresponds to the light source 51, and the light emitted from the lightsource 51 can be transmitted through the quantum dot sheet 57 and can beirradiated.

A width D1 of the region to which the light-converting material 101 isapplied may be variably adjusted.

Specifically, the width D1 of the region to which the light-convertingmaterial 101 is applied may be adjusted according to a distance betweenthe light source 51 and the light guide plate 53, a width of a portionat which the mold frame 15 and the light guide plate 53 are overlapped,and a thickness of the quantum dot sheet 57.

If the width of the overlapping portion of the mold frame 15 and thelight guide plate 53 is small, the amount of the light which is blockedby the mold frame 15 is reduced, so the width D1 of the region to whichthe light-converting material 101 is applied may be decreased. Incontrast, if the width of the overlapping portion of the mold frame 15and the light guide plate 53 is large, the amount of the light which isblocked by the mold frame 15 is increased, so the width D1 of the regionto which the light-converting material 101 is applied may be increased.

If the distance between the light source 51 and the light guide plate 53is large, the amount of the light which is emitted from the light source51 and is directly transmitted through the quantum dot sheet 57 isdecreased, so the width D1 of the region to which the light-convertingmaterial 101 is applied may be decreased. In contrast, if the distancebetween the light source 51 and the light guide plate 53 is small, theamount of the light which is emitted from the light source 51 and isdirectly transmitted through the quantum dot sheet 57 is increased, sothe width D1 of the region to which the light-converting material 101 isapplied may be increased.

Exemplary embodiments are not limited to the configuration in which thelight-converting material 101 is applied to the edge portion at whichthe light source 51 is provided.

As shown in view (b) of FIG. 7, the light-converting material 101 may beapplied to the edge portion at which the light source 51 is notprovided.

At the edge portion of the backlight unit 50 at which the light source51 is not provided, the light emitted from the light source 51 istransmitted through the quantum dot sheet 57 and the optical member 40,but is not irradiated to the outside of the display device 1.

At the edge portion of the backlight unit 50 at which the light source51 is not provided, the light in the light guide plate 53 is irradiatedto a side face of the light guide plate 53 or the light irradiated fromthe light guide plate 53 may be blocked by the mold frame 15. Therefore,there is a lack of light recycling at the edge portion of the backlightunit 50 at which the light source 51 is not provided, and the ratio ofthe white light at the edge portion of the backlight unit 50 at whichthe light source 51 is not provided is less than that at the centralportion of the backlight unit 50. As a result, the image output from thedisplay device 1 looks blue at the edge portion of the display device 1.

For this reason, the light-converting material 101 may be applied to theedge portion of the reflective sheet 55, at which the light source 51 isnot provided as shown in view (b) of FIG. 7. A width D2 of thelight-converting material 101 applied to the edge portion at which thelight source 51 is not provided may be smaller than the width D1 of thelight-converting material 101 applied to the edge portion at which thelight source 51 is provided.

FIG. 8 shows a density of the light-converting material applied to thereflective sheet of the display device according to an exemplaryembodiment.

As previously described, a lack of the light recycling increases fromthe central portion toward the edge portion of the backlight unit 50. Inother words, the light recycling decreases from the center of thebacklight unit 50 toward the edge portion of the backlight unit 50.

In order to compensate for the lack of the light recycling, a density ofthe applied light-converting material 101 may vary according to alocation.

Specifically, since the least amount of light recycling occurs at theedge of the backlight unit 50, causing the strongest monochromatic light(the blue light) to be irradiated and the light recycling is increasedas a distance from the edge of the backlight unit 50 increases so thatthe ratio of the white light is increased, the density of the appliedlight-converting material 101 may be decreased according to a distancefrom the edge portion of the backlight unit 50.

As shown in view (a) of FIG. 8, when the light-converting material 101is applied to the reflective sheet 55 in a circular pattern, thelight-converting material 101 may be applied in the largest circularshape at the edge of the reflective sheet 55 and a circular area of thelight-converting material 101 may decrease as a distance from the edgeof the reflective sheet 55 is increased,

Although not shown in the drawing, the circular area of thelight-converting material 101 may be maintained and a gap between thecircular shapes of the light-converting material 101 may vary. Forexample, the gap between the circular shapes of the light-convertingmaterial 101 applied to the edge of the reflective sheet 55 is narrow,and the gap between the circular shapes of the light-converting material101 may increase as the distance from the edge of the reflective sheet55 is increased.

As shown in view (b) of FIG. 8, the light-converting material 101 havingthe highest concentration may be applied to the edge of the reflectivesheet 55, and the concentration of the light-converting material 101 maybe reduced as the distance from the edge of the reflective sheet 55 isincreased.

By varying the density of the light-converting material 101 according tothe distance from the edge of the backlight unit 50 as described above,it is possible to compensate for the decreased light recycling andprevent reduction of the brightness at the edge portion of the backlightunit 50 by the light-converting material 101.

FIG. 9 shows a pattern of the light-converting material applied to thereflective sheet of the display device according to an exemplaryembodiment.

The light-converting material 101 may be applied in various patterns tothe reflective sheet 55. For example, as shown in view (a) FIG. 8, thelight-converting material 101 may be applied in a circular pattern tothe reflective sheet 55.

As shown in view (a) of FIG. 9, the light-converting material 101 may beapplied in a stripe pattern to the reflective sheet 55. A width of thestripe pattern may be varied according to the distance from the edge ofthe reflective sheet 55. For example, the stripe pattern located at theedge of the reflective sheet 55 has the largest width and the width ofthe stripe pattern may be decreased as the distance from the edge of thereflective sheet 55 is increased.

In addition, the width of the stripe pattern is constantly maintained,but a gap between the stripe patterns may be varied. For example, thegap between the stripe patterns located at the edge of the reflectivesheet 55 is narrowest and the gap between the stripe patterns may beincreased as the distance from the edge of the reflective sheet 55 isincreased.

As shown in view (b) of FIG. 9, the light-converting material 101 may beapplied in a comb pattern to the reflective sheet 55. A length of thecomb pattern may vary according to the distance from the edge of thereflective sheet 55. For example, the length of the comb pattern locatedat the edge of the reflective sheet 55 is longest and the length of thecomb pattern may be shortened as the distance from the edge of thereflective sheet 55 is increased.

In addition, the length of the comb pattern is constant, but a gapbetween the comb patterns may be varied. For example, the gap betweenthe comb patterns located at the edge of the reflective sheet 55 isnarrowest and the gap between the comb patterns may be increased as thedistance from the edge of the reflective sheet 55 is increased.

As shown in view (c) of FIG. 9, the light-converting material 101 may beapplied in a polygonal pattern to the reflective sheet 55. Although view(c) of FIG. 9 shows a rectangular pattern, the shape of the polygonalpattern is not limited thereto, and various patterns such as atriangular pattern, a pentagonal pattern, and the like are available. Anarea of the polygonal pattern may vary according to the distance fromthe edge of the reflective sheet 55. For example, the polygonal patternlocated at the edge of the reflective sheet 55 has the largest area andthe area of the polygonal pattern may be decreased as the distance fromthe edge of the reflective sheet 55 is increased.

In addition, the area of the polygonal pattern is constantly maintained,but a gap between the polygonal patterns may be varied. For example, thegap between the polygonal patterns located at the edge of the reflectivesheet 55 is narrowest and the gap between the polygonal patterns may beincreased as the distance from the edge of the reflective sheet 55 isincreased.

In addition, as shown in view (d) of FIG. 9, the light-convertingmaterial 101 may be applied in an elliptical pattern to the reflectivesheet 55. Although view (d) of FIG. 9 shows the elliptical patternhaving a major axis extending in a horizontal direction, the ellipticalpattern having the major axis extending in a vertical direction or adiagonal direction is available. An area of the elliptical pattern mayvary according to the distance from the edge of the reflective sheet 55.For example, the elliptical pattern located at the edge of thereflective sheet 55 has the largest area and the area of the ellipticalpattern may be decreased as the distance from the edge of the reflectivesheet 55 is increased.

In addition, the area of the elliptical pattern is constantlymaintained, but a gap between the elliptical patterns may be varied. Forexample, the gap between the elliptical patterns located at the edge ofthe reflective sheet 55 is narrowest and the gap between the ellipticalpatterns may be increased as the distance from the edge of thereflective sheet 55 is increased.

FIG. 10 is a graph comparing a color coordinate of the display deviceaccording to an exemplary embodiment with that of a conventional displaydevice.

Specifically, FIG. 10 shows the color coordinate (Y-coordinate)according to a location of the display device 1 according to anexemplary embodiment and the color coordinate (Y-coordinate) accordingto a location of the display device of the conventional art. The displaydevice according to the conventional art is a display device in which alight-converting material (fluorescent material) is not applied to anedge portion of a reflective sheet.

The X-axis in the graph shown in FIG. 10 represents a value obtained bydividing a distance between one side edge and the other side edge of thedisplay device by a width of the display device. In other words, theX-axis represents a relative location with respect to an entire width ofthe display device.

The Y-axis in the graph shown in FIG. 10 represents the color coordinate(Y coordinate) of the light output from the display device. As is widelyknown, the larger the Y coordinate of the color coordinate is, thecloser the light is to the green light end of the spectrum, and thesmaller the Y coordinate of the color coordinate is, the closer thelight is to the blue light end of the spectrum.

One of the points to be noted in FIG. 10 is a deviation of the colorcoordinate (Y coordinate). In other words, if there is a wide deviationbetween the color coordinate (Y coordinate) of the central portion andthe color coordinate (Y coordinate) of the edge portion of the displaydevice, the user U may judge that the central portion differs from theedge portion of the display device based on the color.

Referring to FIG. 10, in the conventional display device, the deviationbetween the color coordinate (Y coordinate) of the central portion andthe color coordinate (Y coordinate) of the edge portion of the displaydevice is approximately “0.013”. In the display device according to anexemplary embodiment, the deviation between the color coordinate (Ycoordinate) of the central portion and the color coordinate (Ycoordinate) of the edge portion of the display device is approximately“0.004”.

Accordingly, compared with the conventional display device, the displaydevice according to an exemplary embodiment has a reduced deviationbetween the central portion and the edge portion.

In particular, compared with the conventional display device, the colorcoordinate (Y coordinate) at the edge portion of the display deviceaccording to an exemplary embodiment is remarkably increased. The ratioof the blue light irradiated from the display device is decreased by thelight-converting material 101 included in the edge portion of thedisplay device 1 according to an exemplary embodiment.

By applying the light-converting material 101 to the edge portion of thereflective sheet 55, it is possible to reduce the deviation of colorbetween the central portion and the edge portion of the display device 1as shown in FIG. 10.

The display device 1 in which the light-converting material 101 isapplied to the edge portion of the reflective sheet 55 to compensate fora lack of the light recycling at the edge portion of the display device1 is described above.

Various display devices compensating for the lack of the light recyclingat the edge portion of the display device are described below.

FIG. 11 shows a side section of a display device according to anexemplary embodiment.

Referring to FIG. 11, a display device 1 a includes the main body 10(11, 13, and 15), the display panel 20, the optical member 40, and abacklight unit 50 a. The main body 10, the display panel 20, and theoptical member 40 are the same as the main body 10 (see FIG. 3), thedisplay panel 20 (see FIG. 3), and the optical member 40 (see FIG. 3) ofthe display device 1 (see FIG. 3) according to an exemplary embodiment.Therefore, the description thereof is omitted.

The backlight unit 50 a includes the light source 51, the light guideplate 53, the reflective sheet 55, the quantum dot sheet 57, and alight-converting material 101 a. The light source 51, the light guideplate 53, the reflective sheet 55, and the quantum dot sheet 57 are thesame as the light source 51 (see FIG. 3), the light guide plate 53 (seeFIG. 3), the reflective sheet 55 (see FIG. 3), and the quantum dot sheet57 (see FIG. 3) of the display device 1 (see FIG. 3) according to anexemplary embodiment. Therefore, the description thereon is omitted.

The light-converting material 101 a is a material which irradiates thevisible light when the light is incident from the outside. Thelight-converting material 101 a may be applied to the edge portion ofthe front surface of the light guide plate 53. Once the light (inparticular, the blue light) is incident, the light-converting material101 a may convert some of the incident light into the yellow light orthe green light and may transmit some of the incident light. As aresult, once the light is incident on the light-converting material 101a, the light-converting material 101 a may irradiate the white lightincluding the blue, yellow, and green lights.

The above light-converting material 101 a may compensate a lack of thelight recycling at an edge portion of the backlight unit 50 a. Inparticular, the light-converting material 101 a applied to the edgeportion of the front surface of the light guide plate 53 may convertlight L13 into the white light. Light L13 is monochromatic light (theblue light) emitted from the light source 51 provided at an edge of thebacklight unit 50 a, and is irradiated to the outside of the displaydevice 1 a through the light guide plate 53 and the quantum dot sheet57. As a result, the light-converting material 101 a may increase theratio of the white light in the light irradiated from the edge portionof the backlight unit 50 a.

As described above, due to the light-converting material 101 a appliedto the edge portion of the front surface of the light guide plate 53,the ratio of the white light in the light irradiated from the edgeportion of the backlight unit 50 a is increased and the deviation of thecolor coordinate between the edge portion and a central portion of thebacklight unit 50 a is decreased.

Although the light-converting material 101 a applied to the edge portionof the front surface of the light guide plate 53 is described in theabove description, the disclosure is not limited thereto, and thelight-converting material 101 a may be applied to the edge portion ofthe rear surface of the quantum dot sheet 57. In other words, thelight-converting material 101 a may be placed between the light guideplate 53 and the quantum dot sheet 57.

FIG. 12 shows a side section of a display device according to anexemplary embodiment.

Referring to FIG. 12, a display device 1 b includes the main body 10(11, 13, and 15), the display panel 20, the optical member 40 and abacklight unit 50 b. The main body 10, the display panel 20, and theoptical member 40 are the same as the main body 10 (see FIG. 3), thedisplay panel 20 (see FIG. 3), and the optical member 40 (see FIG. 3) ofthe display device 1 (see FIG. 3) according to an exemplary embodiment.Therefore, the description thereof is omitted.

The backlight unit 50 b includes the light source 51, the light guideplate 53, the reflective sheet 55, the quantum dot sheet 57, and alight-converting material 101 b. The light source 51, the light guideplate 53, the reflective sheet 55, and the quantum dot sheet 57 are thesame as the light source 51 (see FIG. 3), the light guide plate 53 (seeFIG. 3), the reflective sheet 55 (see FIG. 3), and the quantum dot sheet57 (see FIG. 3) of the display device 1 (see FIG. 3) according to anexemplary embodiment. Therefore, the description thereof is omitted.

The light-converting material 101 b is a material which irradiates thevisible light when the light is incident from the outside. Thelight-converting material 101 b may be applied to the edge portion ofthe front surface of the quantum dot sheet 57. Once the light (inparticular, the blue light) is incident, the light-converting material101 b may convert some of the incident light into the yellow light orthe green light and may transmit some of the incident light. As aresult, once the light is incident on the light-converting material 101b, the light-converting material 101 b may irradiate the white lightincluding the blue, yellow, and green lights.

The above light-converting material 101 b may compensate a lack of thelight recycling at an edge portion of the backlight unit 50 b. Inparticular, the light-converting material 101 b applied to the edgeportion of the front surface of the quantum dot sheet 57 may convertlight L14 into the white light. Light L14 is monochromatic light (theblue light) emitted from the light source 51 provided at an edge of thebacklight unit 50 b, and is irradiated to the outside of the displaydevice 1 b through the light guide plate 53 and the quantum dot sheet57. As a result, the light-converting material 101 b may increase theratio of the white light in the light irradiated from the edge portionof the backlight unit 50 b.

As described above, due to the light-converting material 101 b appliedto the edge portion of the front surface of the quantum dot sheet 57,the ratio of the white light in the light irradiated from the edgeportion of the backlight unit 50 b is increased and the deviation of thecolor coordinate between the edge portion and a central portion of thebacklight unit 50 b is decreased.

FIG. 13 shows a side section of a display device according to anexemplary embodiment.

Referring to FIG. 13, a display device 1 c includes the main body 10(11, 13, and 15), the display panel 20, the optical member 40, and abacklight unit 50 c. The main body 10, the display panel 20, and theoptical member 40 are the same as the main body 10 (see FIG. 3), thedisplay panel 20 (see FIG. 3), and the optical member 40 (see FIG. 3) ofthe display device 1 (see FIG. 3) according to an exemplary embodiment.Therefore, the description thereof is omitted.

In addition, the backlight unit 50 c includes the light source 51, thelight guide plate 53, the reflective sheet 55, the quantum dot sheet 57,and an optical sheet 110 c. The light source 51, the light guide plate53, the reflective sheet 55, and the quantum dot sheet 57 are the sameas the light source 51 (see FIG. 3), the light guide plate 53 (see FIG.3), the reflective sheet 55 (see FIG. 3), and the quantum dot sheet 57(see FIG. 3) of the display device 1 (see FIG. 3) according to anexemplary embodiment. Therefore, the description thereof is omitted.

The optical sheet 110 c is a film formed of a transparent material andmay be provided between the reflective sheet 55 and the light guideplate 53. Also, an edge portion of the optical sheet 110 c may include alight-converting material 111 c. The light-converting material 111 c isa material which irradiates the visible light when the light is incidentfrom the outside. Once the light (in particular, the blue light) isincident, the light-converting material 111 c may convert some of theincident light into the yellow light or the green light and may transmitsome of the incident light. As a result, once the light is incident onthe light-converting material 111 c, the light-converting material 111 cmay irradiate the white light including the blue, yellow, and greenlights.

The above optical sheet 110 c may compensate a lack of the lightrecycling at an edge portion of the backlight unit 50 c. In particular,the light-converting material 111 c included in the edge portion of theoptical sheet 110 c may convert light L15 into the white light. LightL15 is monochromatic light (the blue light) emitted from the lightsource 51 provided at an edge of the backlight unit 50 c and reflectedfrom the reflective sheet 55, and is irradiated to the outside of thedisplay device 1 c. As a result, the optical sheet 110 c may increasethe ratio of the white light in the light irradiated from the edgeportion of the backlight unit 50 c.

As described above, due to the optical sheet 110 c including thelight-converting material 111 c applied to the edge portion thereof, theratio of the white light in the light irradiated from the edge portionof the backlight unit 50 c is increased and the deviation of the colorcoordinate between the edge portion and a central portion of thebacklight unit 50 c is decreased.

FIG. 14 shows a side section of a display device according to anexemplary embodiment.

Referring to FIG. 14, a display device 1 d includes the main body 10(11, 13, and 15), the display panel 20, the optical member 40, and abacklight unit 50 d. The main body 10, the display panel 20, and theoptical member 40 are the same as the main body 10 (see FIG. 3), thedisplay panel 20 (see FIG. 3), and the optical member 40 (see FIG. 3) ofthe display device 1 (see FIG. 3) according to an exemplary embodiment.Therefore, the description thereof is omitted.

In addition, the backlight unit 50 d includes the light source 51, thelight guide plate 53, the reflective sheet 55, the quantum dot sheet 57,and an optical sheet 110 d. The light source 51, the light guide plate53, the reflective sheet 55, and the quantum dot sheet 57 are the sameas the light source 51 (see FIG. 3), the light guide plate 53 (see FIG.3), the reflective sheet 55 (see FIG. 3), and the quantum dot sheet 57(see FIG. 3) of the display device 1 (see FIG. 3) according to anexemplary embodiment. Therefore, the description thereof is omitted.

The optical sheet 110 d is a film formed of a transparent material andmay be provided between the light guide plate 53 and the quantum dotsheet 57. Also, an edge portion of the optical sheet 110 d may include alight-converting material 111 d. The light-converting material 111 d isa material which irradiates the visible light when the light is incidentfrom the outside. Once the light (in particular, the blue light) isincident, the light-converting material 111 d may convert some of theincident light into the yellow light or the green light and may transmitsome of the incident light. As a result, once the light is incident onthe light-converting material 111 d, the light-converting material 111 dmay irradiate the white light including the blue, yellow, and greenlights.

The above optical sheet 110 d may compensate a lack of the lightrecycling at an edge portion of the backlight unit 50 d. In particular,the light-converting material 111 d included in the edge portion of theoptical sheet 110 d may convert light L16 into the white light. LightL16 is monochromatic light (the blue light) emitted from the lightsource 51 provided at an edge of the backlight unit 50 d, and isirradiated to the outside of the display device 1 d through the lightguide plate 53 and the quantum dot sheet 57. As a result, the opticalsheet 110 d may increase the ratio of the white light in the lightirradiated from the edge portion of the backlight unit 50 d.

As described above, due to the optical sheet 110 d including thelight-converting material 111 d applied to the edge portion thereof, theratio of the white light in the light irradiated from the edge portionof the backlight unit 50 d is increased and the deviation of the colorcoordinate between the edge portion and a central portion of thebacklight unit 50 d is decreased.

FIG. 15 shows a side section of a display device according to furtheranother embodiment.

Referring to FIG. 15, a display device 1 e includes the main body 10(11, 13, and 15), the display panel 20, the optical member 40, and abacklight unit 50 e. The main body 10, the display panel 20, and theoptical member 40 are the same as the main body 10 (see FIG. 3), thedisplay panel 20 (see FIG. 3), and the optical member 40 (see FIG. 3) ofthe display device 1 (see FIG. 3) according to an exemplary embodiment.Therefore, the description thereof is omitted.

In addition, the backlight unit 50 e includes the light source 51, thelight guide plate 53, the reflective sheet 55, the quantum dot sheet 57,and an optical sheet 110 e. The light source 51, the light guide plate53, the reflective sheet 55, and the quantum dot sheet 57 are the sameas the light source 51 (see FIG. 3), the light guide plate 53 (see FIG.3), the reflective sheet 55 (see FIG. 3), and the quantum dot sheet 57(see FIG. 3) of the display device 1 (see FIG. 3) according to anexemplary embodiment. Therefore, the description thereof is omitted.

The optical sheet 110 e is a film formed of a transparent material andmay be provided at a front side of the quantum dot sheet 57. Also, anedge portion of the optical sheet 110 e may include a light-convertingmaterial 111 e. Here, the light-converting material 111 e is a materialwhich irradiates the visible light when the light is incident from theoutside. Once the light (in particular, the blue light) is incident, thelight-converting material 111 e may convert some of the incident lightinto the yellow light or the green light and may transmit some of theincident light. As a result, once the light is incident on thelight-converting material 111 e, the light-converting material 111 e mayirradiate the white light including the blue, yellow, and green lights.

The above optical sheet 110 e may compensate a lack of the lightrecycling at an edge portion of the backlight unit 50 e. In particular,the light-converting material 111 e included in the edge portion of theoptical sheet 110 e may convert light L17 into the white light. LightL17 is monochromatic light (the blue light) emitted from the lightsource 51 provided at an edge of the backlight unit 50 e, and isirradiated to the outside of the display device 1 e through the lightguide plate 53 and the quantum dot sheet 57. As a result, the opticalsheet 110 e may increase the ratio of the white light in the lightirradiated from the edge portion of the backlight unit 50 e.

As described above, due to the optical sheet 110 e including thelight-converting material 110 e applied to the edge portion thereof, theratio of the white light in the light irradiated from the edge portionof the backlight unit 50 e is increased and the deviation of the colorcoordinate between the edge portion and a central portion of thebacklight unit 50 e is decreased.

Although exemplary embodiments of the disclosure have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these exemplary embodiments without departingfrom the principles and spirit of the exemplary embodiments, the scopeof which is defined in the claims and their equivalents.

What is claimed is:
 1. A display device, comprising: a display panel; abacklight unit configured to output light to the display panel; and anoptical member configured to refract or reflect the light output fromthe backlight unit and provide the display panel with the refracted orreflected light, wherein the backlight unit comprises: a light sourceconfigured to emit the light; a light guide plate configured toirradiate the light to a first surface of the light guide plate; areflective sheet configured to reflect the light, which is irradiatedfrom a second surface of the light guide plate, to the light guideplate; a quantum dot sheet configured to convert the light, which isirradiated to the first surface of the light guide plate, into a whitelight; and a light-converting material applied to the reflective sheet,only to an at least one edge portion of the reflective sheet, andconfigured to convert the light at the at least one edge portion of thereflective sheet into light capable of being converted to white lightwhen transmitted through the quantum dot sheet.
 2. The display deviceaccording to claim 1, wherein the light-converting material comprises afluorescent material.
 3. The display device according to claim 1,wherein the light-converting material is applied to the reflective sheetin an area defined by a width extending from a first end of thereflective sheet to a central portion of the reflective sheet.
 4. Thedisplay device according to claim 3, wherein an area of the appliedlight-converting material is decreased as a distance from the first endof the reflective sheet is increased.
 5. The display device according toclaim 3, wherein a concentration of the light-converting material isdecreased as a distance from the first end of the reflective sheet isincreased.
 6. The display device according to claim 3, wherein thelight-converting material is applied in a circular pattern to thereflective sheet.
 7. The display device according to claim 3, whereinthe light-converting material is applied in a polygonal pattern to thereflective sheet.
 8. The display device according to claim 3, whereinthe light-converting material is applied in a stripe pattern to thereflective sheet.
 9. The display device according to claim 1, whereinthe light-converting material is further applied to an edge portion ofthe light guide plate.
 10. The display device according to claim 1,wherein the light-converting material is further applied to an edgeportion of the quantum dot sheet.
 11. The display device according toclaim 1, wherein the backlight unit further comprises an optical sheetincluding the light-converting material on an edge portion thereof. 12.The display device according to claim 11, wherein the optical sheet isprovided between the reflective sheet and the light guide plate.
 13. Thedisplay device according to claim 11, wherein the optical sheet isprovided between the light guide plate and the quantum dot sheet. 14.The display device according to claim 11, wherein the optical sheet isprovided between the optical member and the quantum dot sheet.
 15. Abacklight unit comprising, a light source configured to emit light; alight guide plate configured to scatter the light emitted from the lightsource and irradiate the scattered light to a front surface of thebacklight unit; a reflective sheet configured to reflect the light,which is irradiated to a rear surface of the light guide plate, to thelight guide plate; a quantum dot sheet configured to convert the light,which is irradiated to the front surface of the light guide plate, intoa white light; and a light-converting material applied to the reflectivesheet, only to an at least one edge portion of the reflective sheet andconfigured to convert the light at the edge portion of the reflectivesheet into light capable of being converted to white light whentransmitted through the quantum dot sheet.
 16. The backlight unitaccording to claim 15, wherein the light-converting material comprises afluorescent material.
 17. The backlight unit according to claim 15,wherein the light-converting material is applied to the reflective sheetin an area defined by a width extending from a first end of thereflective sheet to a central portion of the reflective sheet.
 18. Thebacklight unit according to claim 17, wherein an area of the appliedlight-converting material is decreased as a distance from the first endof the reflective sheet is increased.
 19. The backlight unit accordingto claim 17, wherein a concentration of the light-converting material isdecreased as a distance from the first end of the reflective sheet tothe central portion of the reflective sheet is increased.
 20. Abacklight unit, comprising: a light source configured to emit light; alight guide plate configured to scatter the light; a reflective sheetprovided on the light guide plate and configured to reflect the light;and a quantum dot sheet configured to output the light as a white light;and a light-converting material applied to the reflective sheet, only toan at least one edge portion of the reflective sheet and configured toconvert the light at the at least one edge portion of the reflectivesheet into the white light.
 21. The backlight unit of claim 20, furthercomprising an optical sheet provided on a front side of the quantum dotsheet and is configured to irradiate visible light.
 22. The backlightunit of claim 21, wherein the light-converting material is provided onone from among the quantum dot sheet, the reflective sheet, and theoptical sheet.
 23. The backlight unit of claim 20, wherein thelight-converting material is provided on an area defined by an edge ofthe backlight unit and a central portion of the backlight unit.
 24. Thebacklight unit of claim 23, wherein the light-converting materialincludes a plurality of circles, the largest circles being at the edgeof the backlight unit and decreasing in size toward the central portionof the backlight unit, with a space between the plurality of circles.